Golang prototype in webassembly

func WasmQueryOn(this js.Value, args []js.Value) interface{} {
	if len(args) > 1 {
		selector := args[0]
		function := args[1]
		if function.Type() == js.TypeFunction && selector.Type() == js.TypeString {
			jsSelector := js.Global().Get("String").New(selector)
			firstLetter := jsSelector.Call("substr", 0, 1)
			firstLetterUpperCase := js.Global().Get("String").New(firstLetter).Call("toUpperCase")
			restOfWord := jsSelector.Call("substr", 1, selector.Length()-1)
			value := "on" + firstLetterUpperCase.String() + restOfWord.String()
			this.Call("addEventListener", value, function)
		}
	}
	return nil
}